While there has been scientific interest in the phenomenon of postpartum depression for many years, only recently has careful, systematic research been undertaken to study this disorder. There is still considerable debate about incidence, course, precursors, and severity of postpartum depression. Moreover, virtually no data exist on the effects of postpartum depression on the developing infant-mother relationship. One purpose of the proposed research is to determine the extent to which pregnancy and the puerperium are associated with a higher than usual risk of depression in women. A large sample of pregnant women and a matched control group of non-pregnant women will be followed through "pregnancy" until "six months postpartum." The incidence, prevalence, and severity of depression in puerperal and non-puerperal women will be compared to determine the true nature of risk of depression associated with pregnancy and the puerperium. Depression and related factors will be assessed through interviews, self-report, and direct observation. These factors include social support, occurrence of stressful life events, personal and family history of psychopathology, psychological attitudes, and several hormones (e.g., cortisol and progesterone) thought to be causally related to postpartum depression. These data will permit us to test hypotheses regarding the importance of both psychosocial and biological causal factors in postpartum depression. Depressed and non-depressed mothers will be observed interacting with their infants about three months after delivery. Specific interactional styles associated with depression in the mother will be identified through careful behavioral analysis. This research will provide information relevant 1) to understanding biological and psychosocial causes of postpartum depression, 2) developing early identification and prevention programs, and 3) developing interventions to enable depressed mothers to interact more effectively with their infants.